1. Field of the Invention
The present invention relates to a method of and apparatus for controlling vacuum pump for use in forming a vacuum in a clean room, etc.
2. Description of the Related Art
A plurality of vacuum pumps are arranged for retaining a vacuum inside a clean room, wherein at least one semiconductor production line is, etc. is prepared. One vacuum pump comprises a pump body for sucking a gaseous body from the clean room, and a driving motor for driving the pump body. After the driving motor rotates, the pump body is activated. Then, the pump body exhaust the clean room of any gaseous body, for example, air and the like.
In the conventional vacuum pumps, the driving motor included in each vacuum pump is directly connected to a commercial power source, for example, a three-phase 200 V power source, and is rotationally driven by a current sent from the commercial power source at a predetermined rotational frequency. According to this conventional structure, too much power has, in many cases, been consumed, thus can not be accomplished to meet the recent demand for saving electric power.
In order to comply with such a demand, it is suggested that the vacuum pumps are controlled as follows: In particular, an inverter is prepared so as to control the rotational frequency of the driving motor included in each vacuum pump. A vacuum degree detecting section is prepared in order to detect the degree of vacuum inside the clean room. In this structure, the frequency of a driving current, which is sent to the driving motor, can be controlled by the inverter with reference to a detection signal output by the vacuum degree detecting section.
In addition to the above-described method, it is also suggested that the inverter for controlling the rotational frequency of the driving motor included in each vacuum pump and a rotational frequency detecting section for detecting the rotational frequency of the driving motor are combined together. In this structure, controlling of the frequency of the driving current, which is sent to the driving motor, may be achieved by the inverter with reference to a detection signal output from the rotational frequency detecting section.
However, even if the driving motor included in each vacuum pump is controlled in the above-described manner, the above-described conventional methods are for maintaining a predetermined degree of vacuum inside the clean room. Therefore, monitoring and determining of whether the vacuum pumps have nearly worn out or not is not performed. Thus, when the vacuum pumps have worn out as a result of a long-term use, the degree of vacuum inside the clean room can not preferably be retained. This result in producing defective semiconductors which are to be produced inside the clean room, causing a great loss of money. In consideration of the above facts, it has been desired that a controlling apparatus, which can retain the degree of vacuum inside the clean room while monitoring whether the vacuum pumps have nearly worn out, is realized.
An object of the present invention is to provide a controlling apparatus for and method of controlling vacuum pump, for achieving protection of vacuum pump, maintaining a degree of vacuum inside a room (e.g., a clean room), and monitoring of whether a driving motor included in each vacuum pump has nearly worn out.
According to the present invention, there is provided a controlling apparatus, for controlling at least one vacuum pump, comprising: at least one vacuum pump which includes a pump body for sucking a gaseous body from a room and exhausting the room of the gaseous body and a driving motor for driving the pump body; and controlling means for controlling the driving motor included in the at least one vacuum pump, and the controlling apparatus including a power measurement device which measures driving power to be sent to the driving motor, and
wherein the controlling means switches a state of the at least one vacuum pump from a steady operational state into an unusual event checking state, in which any unusual event in the at least one vacuum pump is detected, when a value of the power measured by the power measurement device is equal to or exceeds a warning value which is higher than a fixed value.
According to the present invention, there is provided a method of controlling at least one vacuum pump, which comprises a pump body for sucking a gaseous body from a room and exhausting the room of the gaseous body and a driving motor for driving the pump body, the method comprising
switching a state of the at least one vacuum pump from a steady operational state into an unusual event checking state, in which any unusual event in the at least one vacuum pump is detected, when a value of driving power to be sent to the driving motor is equal to or exceeds a warning value, which is higher than a fixed value.